https://s0.wp.com/latex.php?latex=%5Cdisplaystyle+%5Cdfrac%7B%5Cpartial+f%7D%7B%5Cpartial+y%7D%3D%5Cdfrac%7B%5Cpartial%7D%7B%5Cpartial+y%7D%5Cint+M%28x%2Cy%29dx%2Bg%5Cprime%28y%29%3DN%28x%2Cy%29.+%5C+%5C+%5C+%5C+%5C+%285%29&bg=ffffff&fg=000000&s=0&c=20201002